Tiny Planes for Large Tasks

When Boeing builds an airplane, it's big enough for 400 people to board. When Sam Blankenship designs an aircraft, his goal is to make it fit in the palm of his hand.

The jet engines on the aircraft he envisions are the size of shirt buttons. Its flight-control surfaces would flex at the faintest touch of electricity. Its guidance system, two-way radio, video camera, chemical sensors, and the microprocessor commanding them all, would be etched on a single chip.

Carried like a grenade on a GI's belt, such a device could scout out the dangers ahead as a patrol nears a contested town. For about $1,000 to $1,500, a firefighter or rescue worker could buy one to send into a smoke-filled or collapsed building to search for survivors. A real estate agent could loft one to take a quick video of a neighborhood to send to a house-hunting family hundreds of miles away.

For some of these applications, "we're almost there," says an enthusiastic Dr. Blankenship, coordinator of the Microflier research program at the Georgia Institute of Technology in Atlanta. Last month, Georgia Tech hosted the first international conference on micro-air vehicles (MAVs), as the technology is known.

Blankenship acknowledges that when a retired admiral approached him in 1994 with the idea, "I was skeptical." But as he thought about the technical issues and began peering into labs, he says, the answer shifted to "we can do this."

With seed money from the Pentagon's Defense Advanced Research Projects Agency, private and university labs around the United States are pulling the technological threads together to build MAVs.

Among DARPA's goals are craft no more than 15 centimeters (5.9 inches) across, with a range of up to 10 kilometers (6.2 miles) and weight - including sensor payload - of no more than 50 grams (1.8 ounces), researchers say.

These stipulations put more-ambitious versions "in the future, rather than in the present," acknowledges Raphael Haftka, who leads a team of researchers studying aerodynamic issues surrounding MAVs at the University of Florida at Gainesville.

"The small-aircraft field has been dominated by hobbyists," some of whom have developed small and sophisticated designs, he says. "But they achieve their designs by trial and error or some level of analysis" that falls short of the rigor an engineer would apply to optimize a design.

"I'm interested in pushing the state of the art to see what can be done without throwing a lot of money at it." Next month, he is hosting an international flyoff.

Already, elements of MAVs are emerging. These include:

Air frames. Stephen Morris, president of MLB Company, an aerospace consulting firm in Palo Alto, Calif., has built and flown craft that fit the six-inch requirement. They don't qualify as micro-air vehicles, because they don't carry a useful payload, he says. Still, "they represent an important first step. They prove you can control an airplane this size, and they give you a basis for measuring flight performance."

Control surfaces. Using "smart" materials, Ron Barrett of Auburn University in Auburn, Ala., has flown small aircraft whose control surfaces respond directly to electric current, instead of requiring mechanical devices to move them. Known as piezoelectric materials, these ceramics and plastics expand or contract depending on the polarity of the voltage applied to them.

Used as the backbone of a flexible wing, these materials control the aircraft's direction and altitude using only six watch batteries as a power source.

Dr. Barrett, director of the school's adaptive aerostructures lab, says he's shooting for lighter versions that would require only a pair of hearing-aid batteries for energy.

Propulsion. Although some designs use model-airplane engines, researchers are working on more exotic approaches. Jon Sherbeck, director of engineering at MDOT Inc., a Phoenix-based aerospace R&amp;D firm, says his group is "cutting hardware" on a two-ounce jet engine. Measuring about 3 inches long and 1-5/8 inches in diameter, the engine should develop up to 1.4 pounds of thrust, he says. At the Massachusetts Institute of Technology in Cambridge, Alan Epstein, a professor of aeronautics and astronautics, is building a jet engine the size of a shirt button.

Sensor and control systems. Researchers have developed small, light optical and infrared sensors, Blankenship says. His colleagues at Georgia Tech are developing a chip weighing less than a gram that will take those images, process and transmit them, while controlling the rest of the micro-air vehicle. Another team is working on a chip that not only will sense extremely weak concentrations of specific chemicals, but will also detect certain biological compounds.